Electronic devices are generally supplied with power from a power supply unit that converts AC line voltage to a fixed DC voltage. However, various components in such electronic devices may require a different voltage than is supplied by the power supply. Also, some of these components require a highly regulated voltage to operate properly. DC-to-DC converters convert the output of the power supply unit to a different, regulated voltage. For example, a DC-to-DC converter may be required to produce a 5-volt regulated output. In another example, a DC-to-DC converter may need to be capable of providing multiple different voltage levels to multiple different loads. For example, a DC-to-DC converter might need to be capable of providing a 0.8-volt regulated output, a 3.3-volt regulated output, and a 12-volt regulated output.
DC-to-DC converters may be used by a wide variety of electronic devices, such as computers, network cards, and DSL (digital subscriber line) cards. In a computer, the power supply unit may produce one voltage for supply to components (such as disk drives), while another lower voltage is required for the memory chips or processor. It is important in such applications that this lower voltage level be maintained as precisely as possible, because the logic circuitry depends upon voltage levels for accuracy. This is true even when current demands are being placed on the main power supply, such as during start-up when the disk drives are operating and drawing more power than usual.
An isolated power converter is a power converter in which the input referred ground is physically disconnected from the output referred ground. Isolated DC-to-DC power converters include a transformer that provides a barrier between the input-side voltage and output-side voltage. This transformer provides a measure of safety, because the barrier can withstand high input voltages. In some isolated converters, transient response, typically to load steps, is limited by the leakage inductance of the transformer itself. This is especially an issue with hard-switched full-bridge and phase-shifted full-bridge converters. As a consequence of the limited transient response performance, these types of converters have not yet been applied to very dynamic loads, such as CPUs.